This is a 36 pages long doujin, that as the other works from this circle is also mostly centered in comedy. This time the people close to the Takamachi family notices the sudden gain in weight that Fate and Vivio are getting lately, and probably you are imagining already who we can blame for this.
"Sorry for Being so Sweet!" follows the line (of most) of the other works from this circle: you will see some hilarious NanoFate and family moments, a lovers' quarrel, and maybe even learn a bit about Japanese gastronomy.
Vivio runs with Einhart to the beach, and Nanoha and Fate look after them